A conventional roller or wheel W secured with a hub H is rotatably mounted on an axle A of a roller skate as shown in FIGS. 1 and 2, in which the roller or wheel W may be made of polyurethane (PU) or polyvinyl chloride (PVC) material. However, such a conventional roller has the following drawbacks:
1. Even polyurethane, for instance, may have good elasticity and resistance to abrasion, but is generally considered to be less resistant to high or low temperature. During a high-speed running of a skate roller, a frictional heat may be produced to deteriorate or damage such PU rollers.
2. In order to reinforce the strength and stability of the PU roller, a rigid central hub H with extension E is integrally secured with the ring-shaped wheel W. Since the wheel W may be made of elastomer foam material, a poor foam product such as unhomogeneous porosity or shrunk molding product will cause instability of the wheel when running the roller skate or even cause sport accident or injury to a player.
3. The wheel W is integrated with hub H so that once the wheel W is damaged the whole wheel unit should be deleted to waste resource.
4. The hub H is merely a circular-shaped disk, having no clamping portions for efficiently clamping the wheel W, so that the wheel unit will be vibrated when gliding a roller skate to thereby influence a stable playing of the skate since the hub H is formed as a "flat" disk without having any clamping flanges provided thereon for clamping the wheel W.
5. No tread grooves exist in the wheel surface to easily cause slipping on a ground surface, also lacking of waterrepelling capability.
The present inventor has found the drawbacks of the rollers or wheels of a conventional roller skate and invented the present wheel having better properties.